nginx [engine x] is a HTTP and reverse proxy , as well as a mail proxy written by Igor Sysoev. It has been running for more than five years on many heavily loaded Russian sites including Rambler (RamblerMedia.com). According to Netcraft erved or proxied 4.24% busiest sites in January 2010. Here are some of success stories: FastMail.FM, WordPress.com.

I have tried it and it is a must!